摘要:

AbstractThe frequency of labeled mitoses method (FLM) was used to study the cell kinetics in the stratified squamous epithelium of the mouse esophagus and tongue. FLMs were generated by injecting tritiated thymidine (TdR) at two different phases of the mouse circadian system: TdR was injected into one group of mice at 0900 and into a different, second group of mice at 2100. Three variables were monitored for each group; (1) the FLM, (2) the mitotic index and (3) the grain count over the labeled mitotic figures. In both the esophagus and the tongue there was a circadian rhythm in the mitotic index with the peak occurring during the first half of the diurnal phase and the trough occurring during the first half of the nocturnal phase. The FLM curves from each group revealed the following data:TextTransit time in G2+1/2M(TG2+1/2M)Transit time in S phase (TS)hourshoursEsophagus — TdR at 09002.55.3Esophagus — TdR at 21004.53.5Tongue — TdR at 09004.25.1Tongue — TdR at 21004.25.5Second waves of labeled mitoses were seen in the esophagus and tongue when TdR was injected at 0900. No second wave of labeled mitoses occurred in either the esophagus or the tongue when TdR was injected at 2100. For the esophagus the grain counts of the labeled mitotic figures in each group indicated that the rate of DNA synthesis was greater during late S phase, whether the TdR was injected at 0900 or 2100. During most of the S phase the rate of DNA synthesis was significantly greater in the TdR at 2100 group, which is the time of the circadian system when the esophagus demonstrated a relatively short Ts. In the epithelium of the tongue there were a few statistical differences in the rate of DNA synthesis between the groups and during the duration of the S phase within either group, but these data were difficult to interpret.The data demonstrate the influence of the circadian system in cell kinetic work and in the interpretation of data obtained with the FLM in renewing populations of cells which are not totally async

ISSN:0003-276X    

DOI:10.1002/ar.1091840302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractA circadian rhythm in the incorporation of tritiated thymidine into DNA of the mouse thymus has been described. This same rhythm in animals bearing an 8‐day Ehrlich ascites tumor (EAT) was altered in its phasing, wave‐form and over‐all 24‐hour mean; the most striking alteration seen in four out of five studies was a reduction in the over‐all DNA synthesis rate in tumor‐bearing animals.Mice subjected to an altered light‐dark cycle did not show a complete phase shift in their thymus DNA rhythm within two weeks, but during this time the rhythm in the mitotic index of their corneal epithelium completely phase shifted; the presence of the tumor had no effect on this latter rhythm. In mice subjected to a daily 4‐hour restricted feeding schedule, the rhythm in DNA synthesis in the thymus became synchronized in that the peak occurred toward the end of the 4‐hour restricted feeding span in both tumor and non‐tumor‐bearing animals. The rhythm in the mitotic index in the cornea was not phase shifted or altered by the restricted meal timing.The DNA synthesis rhythm in the normal thymus demonstrated a phasing similar to (1) the rhythm in the length of survival time in untreated mice challenged with EAT and (2) the rhythm in DNA synthesis

ISSN:0003-276X    

DOI:10.1002/ar.1091840303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe in vitro incorporation of3H‐5‐uridine into the germinal and somatic cells of the larval ovary ofXenopus laevishas been studied using both light and electron microscope autoradiography. Incubation for only one hour in the presence of precursor revealed that the follicle cells are highly active in rRNA synthesis, whereas substantial oogonial nucleolar labeling was not detected for several hours. Semi‐quantitative analysis of high‐resolution autoradiograms indicated that the density of silver grains associated with “nuage” in oogonia was almost 4‐fold greater than the surrounding cytoplasm. This strongly suggests that a significant amount of RNA is associated with “nuage” at this stage ofXenopusoogenesis, in addition to its well documented protein composition. “Pulse‐chase” experiments further suggest that the nuage‐associated RNA is stable for at least 24 hours. These results are discussed (within the limitations imposed by the methodology) both in relation to other studies on the composition of nuage in a wide variety of germinal cell types and in the light of growing speculation that nuage and germina

ISSN:0003-276X    

DOI:10.1002/ar.1091840304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractSubmandibular glands from 17‐day‐old rat fetuses were maintained in organ culture for five days in a medium consisting of Eagle's MEM (87%), horse serum (10%), and chick embryo extract (3%). Each day of the culture period explants were incubated for the demonstration of peroxidase activity and processed for light and electron microscopic observations. In some experiments cultures were exposed to3H‐thymidine one hour prior to fixation and incubation for the demonstration of peroxidase activity. Labelling index was determined using radioautographs of 1 μ Epon‐embedded sections. At the time of explantation the submandibular gland rudiment consisted of undifferentiated epithelial cells arranged in cords. On day 3 of culture two additional cell types could be distinguished: terminal tubule cells and proacinar cells. The proacinar cells were characterized by peroxidase activity in their granules and cytoplasm. By day 4 acinar cells begin to appear. On the fifth day of culture the four cell types of the terminal tubule were present in the following proportions: undifferentiated cells, 44%; terminal tubule cells, 19%; proacinar cells, 31%; acinar cells, 6%. These results indicate that the cytodifferentiation of the secretory unit of rat submandibular gland in vitro is comparable to the differentiation

ISSN:0003-276X    

DOI:10.1002/ar.1091840305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractAdult male mice were exposed to either alternating illumination or constant illumination for 70 days. Light and dark pinealocytes were compared as to distribution within the gland and ultrastructure. Quantitative studies with the electron microscope revealed a significant reduction in pinealocyte size and Golgi complex size in constant light treatment, as well as a marked but non‐significant reduction in the concentration of lipid droplets and irregular vacuoles. Under constant light treatment the cross‐sectional area of pinealocyte pericapillary terminals and the number of granulated vesicles per terminal decreased significantly. A greater number of mitochondria appeared swollen, with rarified matrix and reduced numbers of cristae, with constant light treatment.These results provide ultrastructural correlation with the known reduction of pineal weight, protein synthesis and antigonadotrophic activity that is seen with constant light treatment. The marked decrease in concentration of pinealocyte granulated vesicles in constant light treatment gives morphological support to the theory that these vesicles contain antigonadotrophic secretory mater

ISSN:0003-276X    

DOI:10.1002/ar.1091840306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe effects of neonatal thymectomy on the development of the lymphoid, erythroid and granulocytic cell populations in mouse bone marrow have been assessed by quantitative techniques. The numbers per unit volume of bone marrow of 17 cell types were determined in neonatally thymectomized and sham thymectomized C3H mice at two, four and eight weeks of age, and compared with those of normal C3H mice. After neonatal thymectomy the numbers of small lymphocytes, large and medium‐sized lymphoid cells, and erythroid cells reached normal levels at two weeks but fell progressively to 18%, 22% and 42% of normal, respectively, by eight weeks. In sham thymectomized mice these cell populations did not differ significantly from normal. Immature and mature granulocytes were elevated in numbers two weeks after either neonatal thymectomy or sham thymectomy, suggesting a transient non‐specific stimulation of granulocytopoiesis. During continuous infusion of3H‐thymidine for ten days in neonatally thymectomized mice aged four weeks and eight weeks many bone marrow small lymphocytes remained unlabeled. The results demonstrate that early postnatal development of bone marrow lymphoid and erythroid cells proceeds normally in the absence of the thymus, in accord with the concept of the bone marrow as a primary site of lymphocyte production and differentiation. In addition, some slowly‐renewing small lymphocytes in bone marrow appear to be thymus‐independ

ISSN:0003-276X    

DOI:10.1002/ar.1091840307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

ISSN:0003-276X    

DOI:10.1002/ar.1091840308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

ISSN:0003-276X    

DOI:10.1002/ar.1091840301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY